Multi carburetor system of variable area venturi type with auxiliary fuel supply system

ABSTRACT

An auxiliary fuel supply system for use in a multi carburetor system of the variable area venturi type for an internal combustion engine of a motor vehicle. The auxiliary fuel supply system consists of a body having formed therein a main mixture passage, a slow running mixture circuit and a deceleration circuit. The main mixture passage is connected to intake manifolds of the engine. The slow running mixture circuit has a slow running port communicating with the main mixture passage for supplying the engine with an air-fuel mixture of optimum air-fuel ratio during low speed and light loud operations of the engine. The deceleration mixture circuit has a deceleration port which communicates with the main mixture passage for supplying the engine with an air-fuel mixture of optimum for decelerating condition of the engine. The auxiliary fuel supply system also consists of a control unit having diaphragm means responsive to an intake manifold vacuum of the engine and a valve element attached to the diaphragm means and extending into the deceleration circuit to open and close the deceleration port, the diaphragm means being moved to a position to cause the valve element to open the deceleration port when the intake manifold vacuum reachs a predetermined value.

United States Patent [1 1 Hisatomi et al.

[ MULTI CARBURETOR SYSTEM OF VARIABLE AREA VENTURI TYPE WITH AUXILIARY FUEL SUPPLY SYSTEM I 75] lnventors:Takashi Hisatomi; Kenichi Sasaki, both of Yokohama. Japan [73] Assignee: Nissan Motor Company, Limited,

Yokohama, Japan [22] Filed: Mar. 10, 1972 [2]] Appl. No.: 233,603

Primary Examiner-Wendell E. Burns Att0rney.lohn Lezdey [451 July 3,1973

[5 7] ABSTRACT An auxiliary fuel supply system for use in a multi carburetor system of the variable area venturi type for an internal combustion engine ofa motor vehicle. The auxiliary fuel supply system consists of a body having formed therein a main mixture passage, a slow running mixture circuit and a deceleration circuit. The main mixture passage is connected to intake manifolds of the engine. The slow running mixture circuit has a slow running port communicating with the main mixture passage for supplying the engine with an air-fuel mixture of optimum air-fuel ratio during low speed and light loud operations of the engine. The deceleration mixture circuit has a deceleration port which commu nicates with the main mixture passage for supplying the engine with an air-fuel mixture of optimum for decelerating condition of the engine. The auxiliary fuel supply system also consists of a control unit having diaphragm means responsive to an intake manifold vacuum of the engine and a valve element attached to the diaphragm means and extending into the deceleration circuit to open and close the deceleration port, the diaphragm means being moved to a position to cause the valve ele ment to open the deceleration port when the intake manifold vacuum reachs a predetermined value.

8 Claims, 5 Drawing Figures PATENTED JUL 3 I973 SREEV 1 BF 2 VEH ICLE SPEED PATENIEDJUL3 ms 3.742.922

sum 2 III 2 TO INTAKE MAN I FO LD Fig. 5

AIR FUEL RATIO VEHICLE SPEED 1 MULTI CARBURETOR SYSTEM OF VARIABLE AREA VENTURI TYPE WITH AUXILIARY FUEL SUPPLY SYSTEM This invention relates in general to a carburetor for an internal combustion engine of a motor vehicle and,

. more particularly, to a multi carburetor system of the variable area venturi type equipped with an auxiliary fuel supply system which is capable of supplying the engine with an air-fuel mixture of optimum air-fuel ratio that is specifically suited for idling and decelerating opetions of the engine.

In a motor vehicle driven by an internal combustion engine equipped with a multi carburetor system of the variable area-venturi type, problems have heretofore been experienced from the fact that it is quite difficult to adjust the air-fuel ratio of an air-fuel mixture to be supplied to the engine to meet varying operating conditions of the engine because of the inherent construction of idling adjusting system of the carburetor system. Therefore, it has heretofore been proposed to provide an additional fuel supply system, called the idling and slow running mixture circuit, in the multi carburetor system of the variable area venturi type to supply an auxiliary air-fuel mixture to the engine during idling and decelerating operations in an amount and mixture ratio that are predetermined. Under this circumstance, a difficulty is still encountered on the engine which is specifically equipped with a multi carburetor system of the variable area venturi type in that the air-fuel mixture can not be uniformly distributed to the several engine cylinders. Moreover, the engine is supplied during deceleration with an air-fuel mixture which is predetermined to enable the engine to operate satisfactorily during the idling, not the decelerating operation. This is reflected by reduced combustion efficiency and misfiring in the combustion chambers of the'engine during deceleration so that a certain unburned content which is largely hydrocarbons is emitted to the atmosphere causing serious air pollution especially in urban areas.

To solve the vehicular air pollution problem to be traced to the unburned toxic content of engine exhaust gases, the present invention contemplates to provide an auxiliary fuel supply system specifically suited for use in a multi carburetor system. The auxiliary fuel supply system largely consists of a slow running mixture circuit and a deceleration mixture circuit which are adapted to provide air-fuel mixtures of optimum amounts and mixture ratios that are suited for idling and decelerating operations, respectively. It is, therefore, an object of the present invention to provide an auxiliary fuel supply system for use in a multi carburetor system of the variable area venturi type of an internal combustion engine for a motor vehicle, which fuel supply system is capable of supplying the engine with an air-fuel mixture of optimum mixture ratio that is specifically suited for idling operation of the engine.

Another object of the present invention is to provide an auxiliary fuel supply system for use in a multi carburetor system of the variable area venturi type, which system is capable of supplying the engine with an airfuel mixture of optimum mixture ratio that is specifically suited for decelerating operation of the engine.

Astill another object of the present invention is to provide an auxiliary fuel supply system for use in a multi carburetor system of the variable area venturi type, which system is adapted to eliminate the unburned content in engine exhaust gases emitted to the atmosphere during idling and deceleration of the engine.

A further object of the present invention is to provide an auxiliary fuel supply system which is readily adaptable to existing multi carburetor systems of the variable area venturi type now in use.

A still further object of the present invention is to provide an auxiliary fuel supply system for use in a multi carburetor system of 'the variable area venturi type, which system is simple in construction and economical to manufacture.

In general, these objects of the present invention can be achievedby an auxiliary fuel supply system which is I associated with a multi carburetor system of the variable area ventrui type to provide the engine with an airfuel mixture of optimum air-fuel ratio for the idling and deceleration operations of the engine. The auxiliary fuel supply system includes a body in which a main mixture passage is formed, which is connected to the intake manifolds of the engine through a balance tube extending therebetween. The main mixture passage has formed with a main'air inlet passage leading from an air chamber communicating with an air cleaner of the multi carburetor system. A main adjust screw is provided in the main air inlet passage to control the flow of air passing therethrough. Thebody of the auxiliary fuel supply system is also formed with a slow running mixture circuit having a slow running port communicating with the main mixture passage formed in the body. A slow running adjust screw is provided in the slow running port to control the amount of idling airfuel mixture passing therethrough. The slow running mixture circuit has a slow running air bleed and a slow running fuel jet provided upstream of the slow running air bleed. The effective areas of the slow running air bleed and the slow running fuel jet are so determined to provide an air-fuel mixture of optimum air-fuel ratio for the low speed and light load operations of the engine The auxiliary fuel supply system also includes a deceleration mixture circuit having a deceleration circuit communicating with the main mixture circuit. The deceleration mixture circuit is formed at its upstream side with a deceleration air bleed, which communicates with the air chamber. A deceleration fuel jet is provided in the deceleration mixture circuit downstream of the deceleration air bleed, the deceleration fuel jet being connected to a fuel supply chamber formed in the body. To control the amount of deceleration airfuel mixture supplied through the deceleration port, a control unit is provided on the body of the auxiliary fuel supply system. The control unit consists of first and second diaphragm means operatively disposed in first and second vacuum chambers, respectively. The first diaphragm means has attached thereto a first valve element which is operatively inserted in a valve opening formed in a wall portion intervening between the first and second vacuum chambers to selectively open and close the valve opening for thereby interconnecting and disconnecting the first and second vacuum chambers from each other. A first compression spring is disposed in the first vacuum chamber for biasing the first diaphragm means to a position in which the first valve element close the valve opening to interrupt communication between the first and second vacuum chambers. The first vacuum chamber is connected through an out let passage with the main mixture passage communicating with the intake manifolds of the engine and is subjected to the intake manifold vacuum. The second diaphragm means has attached thereto a second valve element which extends into the deceleration circuit to open and close the deceleration port. A second compression spring is disposed in the second vacuum chamber for biasing the second diaphragm means to a position in which the second valve element closes the deceleration port. When the intake manifold in the first vacuum chamber reaches a predetermined value, the pressure difference on opposite sides of the first diaphragm means will be sufficient to overcome the biasing force of the first compression spring and the first diaphragm means will move to a position to cause the first valve element to open the valve opening. Upon opening of the valve opening, the second vacuum chamber will be subjected to the intake manifold vacuum, and the pressure difference on opposite sides of the second diaphragm means will effect movement of the second diaphragm means so as to cause the second valve element to open the deceleration port. When the deceleration port is open, the air in the air chamber is sucked in the deceleration circuit through the deceleration air bleed due to the intake manifold vacuum. The air flowing across the deceleration fuel jet will create a suction effects which causes a flow of fuel from the fuel supply chamber into the air stream which is being supplied to the main mixture passage through the deceleration circuit. Thus, the air is mixed with the fuel, and the resulting air-fuel mixture supplied from the deceleration circuit plus idling air-fuel mixture flowing through the slow running port is combustible to eliminate unburned engine exhaust gases emitted to the atmosphere during deceleration of the engine.

These and other features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic sectional view ofa conventional multi carburetor system of the variable area venturi type to which an auxiliary fuel supply system of the present invention is to be applied;

FIG. 2 is a graph showing the relationship between the air-fuel ratio determined under varying vehicle speeds which are obtained in the conventional carburetor system shown in FIG. 1;

FIG. 3 is a schematic view of the multi carburetor system of the variable area venturi type incorporating the auxiliary fuel supply system according to the present invention;

FIG. 4 is a sectional view ofa preferred embodiment of the auxiliary fuel supply system used in the multi carburetor system of FIG. 3; and

FIG. 5 is a graph showing an example ofa desired relationship between the air-fuel ratio of the air-fuel mixture and the vehicle speed.

Referring now to FIG. 1, there is shown in section a conventional multi carburetor system of the variable area venturi type, only one carburetor being shown in FIG. 1 for air flow sake of simplicity of illustration. The carburetor, which is generally designated by reference numberal 10, largely consists of, as customary, a carburetor body 12, a carburetor induction passage 14 formed in the carburetor body 12, the carburetor induction passage 14 leading from an air cleaner (not shown) and leading into an intake manifold (not shown) of the engine, a throttle valve 16 operatively disposed in the carburetor induction passage 14 for controlling the flow of an air-fuel mixture to be supplied to the engine, and a variable area venturi 18 consisting of a constriction or bridge 20 and an airflow control assembly 22.

The carburetor 10 also consists of a main fuel jet 24 which is slidably received in a bore (not identified) formed in the carburetor body 12 and which is in communication with a float chamber (not shown) through an opening 26. The main fuel jet 24 opens into the carburetor induction passage 14 at the constriction 20 of the variable area venturi 18 for supplying liquid fuel thereinto. An idle mixture adjusting nut 28 is threaded on to the lower end of the fuel jet 24. In adjusting the idle mixture, the nut 28 is turned in the required direction, so that the main fuel jet 24 is moved upwardly or downwardly to meter the required idling mixture.

The air flow control assembly 22 comprises a casing 30 having formed therein a suction chamber 32 and a suction piston 34 which is slidably disposed in the suction chamber 32. A suction channel 36 is formed in the bottom wall of the suction piston 34 to admit the subatomspheric pressure prevailing around the venturi 18 into the suction chamber 32 so that the suction piston 34 is moved upwardly to increase the effective area of the venturi 18. A compression spring 38 is disposed in the suction chamber for biasing the suction piston 34 in its closed position.

To limit undue movement of the suction piston 34 and to retard its upward travel in acceleration and so enrich the mixture for this condition, a dumper plunger 40 is suspended by a rod 42 from a dumper cap (not identified) in an oil-filled chamber 44. Indicated at 46 is an air vent which permits smooth upward and downward movements of the suction piston 34.

To control the effective area of a metering orifice of the main fuel jet 24, a metering needle 48 is provided which is secured in the bottom wall of the suction piston 34 and which is inserted into through the metering orifice into the fuel jet 24. The metering needle 48 is tapered toward its tip for continuously changing the amount of liquid fuel to be admitted into the venturi 18 as the suction piston 34 and accordingly the metering needle 48 move upwardly and downwardly in response to the fluctiations in the intake manifold to thereby vary the effective venturi area into which the liquid fuel is drawn from the fuel jet 24.

With this arrangement, the air-fuel ratio of the airfuel mixture for the idling operation is controlled, in the conventional carburetor 10, by changing the position of the main fueljet 24 relative to the metering needle 48. Such position of the fuel jet 24 critic critically dictates the air-fuel ratio during engine operating conditions other than idling so that it is extremely difficult to supply the engine with an air-fuel mixture of an optimum air-fuel ratio during the idling operation without sacrificing the air-fuel ratios optimum for other operating conditions of the engine. This is exemplified in the graph of FIG. 2, wherein air-fuel ratio is plotted in terms of varying vehicle speeds.

During deceleration of the engine with the throttle valve 16 closed when the vehicle is driving the engine, the intake manifold vacuum increases appreciably above the intake manifold vacuum created during all normal running operations of the engine. When this occurs, the quantity of air flowing around the closed throttle valve is insufficient to clean out the exhaust gases from the engine cylinders, and consequently the air-fuel mixture supplied through the variable area venturi 18 will not completely burn to increase the unburned content in the engine exhaust gases thereby causing serious air pollution especially in urban areas. Accordingly, it has heretofore been proposed to supply additional air either directly to the intake manifolds or through the throttle valve by suitable means. While this arrangement appears to present a solution to the problem by leaning out the air-fuel mixture supplied to and purging exhaust gases from the engine cylinders during deceleration, no means have been devised to adjust the air-fuel ratio of the air-fuel mixture to be supplied to the engine to an appropriate value for satisfactory combustion.

The present invention proposes to provide an auxiliary fuel supply system especially suited for use in a multi carburetor systemof the variable area venturi type, the auxiliary fuel supply system being adapted to calibrate the additional air and fuel to provide combustible air-fuel mixtures suited for the idling and decelerating operations of the engine. The auxiliary fuel supply system, which is generally represented by reference numeral 50, is herein shown as interposed at an intermediate portion of a balance tube 52 which extends between the intake manifolds, designated at 54 in FIG. 3, of the internal combustion engine 56(see FIG. 3).

Referring next to FIG. 4, there is shown in section a detail construction of a preferred embodiment of the auxiliary fuel supply system 50 implementing the present invention. As shown, the present system 50 includes a body 58 which may be mounted on the balance tube 52 of the carburetor in known fashion. A main mixture passage 60 is formed in the body 58 and communicates at the downstream side thereof with the intake manifolds 54 of the engine 56 through the balance tube 52. The main mixture passage 60 communicates at its upstream side with a main air inlet passage 62 leading from an air chamber 64, which communicates with an air pipe 66 leading to the air cleaner 68 (see FIG. 3). A main adjust screw 70 is threaded on the body 58, the screw 70 extending into the main air inlet passage 62 to meter the amount of air passing therethrough.

As shown in FIG. 4, the auxiliary fuel supply system 50 also includes slow running mixture circuit 72 for supplying the engine with an air-fuel mixture of optimum air-fuel ratio during idling and light load operations. The slow running mixture circuit 72 opens to the main mixture passage through a slow running port 74, of which effective area is adjusted by a slow running adjust screw 76 screwed into the body wall. Indicated at 78 is a slow running air bleed which is vented to the atmosphere and which is so sized in diameter as to admit a suitable amount of air to the slow running mixture circuit 72. A slow running fuel jet 80 is provided in the slow running mixture circuit 72 upstream of the slow running air bleed 78, the fuel jet 80 having first and second orifices 80a and 80b for metering the amount of liquid fuel to be admitted to the slow running mixture circuit 72. The first orifice 80a of the slow running fuel jet 80 opens to a fuel supply chamber 82 formed in the body 58, the fuel supply chamber communicating with the float chamber, designated at 84 in FIG. 3, through a coupling 86.

The auxiliary fuel supply system 50 further includes a deceleration mixture circuit 88 having a deceleration air bleed 90 opening to the air chamber 64 and having a deceleration fuel jet 92 provided in the deceleration circuit 88 downstream of the deceleration air bleed 90. The deceleration fuel jet 92 communicates with the fuel supply chamber 82 through a deceleration fuel supply passage 94. The deceleration mixture circuit 88 also has a deceleration port 96 formed therein which opens to the main mixture passage 60 for supplying the air-fuel mixture therethrough to the intake manifolds of the engine. The effective areas of the deceleration air bleed 90 and the deceleration fuel jet 92 are so determined as to admit suitable amount of air and fuel whereby the air-fuel mixture flowing through the deceleration port 96 is mixed with the idle air-fuel mixture supplied through the slow running port 74 to form a combustible air-fuel mixture.

To control the deceleration port 96, a control unit 98 is further provided in the auxiliary fuel supply system 50. Thecontrol unit 98 consists of a housing 100 having formed with first and second cavities 102 and 104, which are separated from each other by means of a wall portion 106. The first and second cavities 102 and 104 act as vaccum chambers, respectively, as will be discussed hereinafter in detail. The wall portion 106 is formed at its central portion with a valve opening 108 which interconnects the first and second vacuum chambers 102 and 104 with respect to each other. The first vacuum chamber 102 is connected through an outlet passage 110 to the main mixture. passage 60, which in turn is connected to the intake manifolds 54 of the engine.

The one end of the housing 100 is closed by a cap member 112, a first diaphragm member 114 being interposed between the cap member 112 and the one end of the housing 100. The cap member 112 is attached to the one end of the housing 100 by a known suitable fastener means, though not shown. The cap member 112 has formed with a central aperture 116 constituting an atmospheric vent for the chamber formed between the first diaphragm member 114 and the inner surface of the cap member 112. The first diaphragm member has attached thereto a disc assembly 118 by means of a first valve element 120 with an enlarged tip. The first valve element 120 extends through the valve opening 108 formed in the wall portion 106 to open or close the same for thereby providing or interrupting communication between the first and second vacuum chambers 102 and 104. A first coiled compression spring 122 is disposed in the first vacuum chamber 102 for biasing the first diaphragm member rightwardly of the drawing to a position in which the first valve element closes the valve' opening 108. The one end of the compression spring 122 engages with one side of the wall portion 106 while the other end of the compression spring 122 engages with one disc of the disc assembly 118. The resisting spring load on the first diaphragm member 114 is adjusted so that this diaphragm member is not actuated until the intake manifold vacuum exceeds a predetermined value.

As seen in FIG. 4, the other end of the housing 100 is secured to the side wall of the body 58 by a known suitable fastener means (not shown). A second diaphragm member 124 is interposed between the side wall of the body 58 and the other end of the housing 100 and has attached. thereto a disc assembly 126 by means of a second valve element 128. The second valve element 128 is provided with a conical tip at its terminal end and extends through an opening 130 formed in the side wall of the body 58 into the deceleration circuit 88 to open and close the deceleration port 96. A second coiled compression spring 132 is disposed in the second vaccum chamber 104 for biasing the second diaphragm member 124 leftwardly, as viewed in FIG. 4, to a position in which the second valve element closes the deceleration port 96. The one end of the compression spring 132 engages with one disc of the disc assembly 126 while the other end of the spring 132 engages with the other side of the wall portion 106.

The housing also has formed therein a bore 134, which interconnects the second vacuum chamber 104 with the atmosphere through a calibrated air bleed 136. The calibrated air bleed 136 prevents the trapping of vacuum in the second vacuum chamber 104 when the first valve element 120 opens the valve opening 108 so that the second diaphragm member 124 will respond quickly and in a follow-up manner to the movements of the first diaphragm member 114. It is should be appreciated that in the illustrated embodiment, the bore 136 is herein shown as communicating with the air chamber 64 but may be constituted to directly open to the atmosphere. A chamber 138 formed between the side wallof the body 58 and the second diaphragm member 124 is interconnected to the air chamber 64 through a passage 140 for effecting smooth movement of the second diaphragm member 124. The chamber 138 is also interconnected to the outlet passage 110 through an orifice 142, which permits the air-fuel mixture flowing into the chamber 138 through the opening 130 to pass into the outlet passage 110.

When assemblying the auxiliary fuel supply system 50 of the present invention to the conventional multi carburetor system of the variable area venturi type 10, the throttle valve 16 is arranged to be fully closed during idling and decelerating conditions of the engine. Moreover, the idling adjust nut 28 is turned in a direction to maintain the jet orifice of the main fuel jet 24 in a position appropriate for providing an air-fuel mixture of optimum air-fuel ratio during high speed and heavy load opeations of the engine. The air-fuel ratios of the air-fuel mixtures for the idling and declerating operations of the engine can be adjusted by turning the main adjust screw 70 and the slow running adjust screw 76 in their desired directions so that the air-fuel ratios of the air-fuel mixtures to be supplied to the engine can vary in a manner as shown in FIG. 5, wherein air-fuel ratio is plotted in terms of vehicle speed.

During normal idling operation of an engine equipped with the auxiliary fuel supply system according to the present invention, the throttle valve is fully closed so that low intake manifold vacuum prevails in the intake manifolds 54 of the engine. Since, in this instance, the main mixture passage 60 is connected through the balance tube 52 (see FIG. 3) to the intake manifold 54, the main mixture passage 60 is subjected to the vacuum in the intake manifolds 54. When this occurs, the liquid fuel in the fuel supply chamber 82 is drawn through the slow running fuel jet 80 into the slow running circuit 72 and the air is also admitted into the slow running mixture circuit 72, the air being mixed with the liquid fuel drawn from the fuel jet 80 to form an idling air-fuel mixture of optimum air-fuel ratio. The air-fuel mixture thus formed is then supplied through the slow running port 74 into the main mixture passage 60, through which the idling air-fuel mixture is distributed to the intake manifolds 54 leading to the engine cylinders (not shown).

During decelerating operation of the engine with the throttle valve fully closed and the engine driven by the motor vehicle, the intake manifold vacuum increases appreciably above the intake manifold vacuum created during the idling operation of the engine. When the intake manifold vacuum reaches a predetermined value, the pressure difference on opposite sides of the first diaphragm member 114 will be sufficient to overcome the biasing force of the first compression spring 122 and the first diaphragm member 114 will move leftwardly, as viewed in FIG. 4, to cause the first valve element 120 to open the valve opening 108. Upon opening of the valve opening 108, the second vacuum chamber 104 will be subjected to the intake manifold vacuum, and the pressure difference on opposite sides of the second diaphragm member 124 will effect movement of the second diaphragm member 124 against the biasing force of the second compression spring 132 to cause the second valve element 128 to open the deceleration port 96. Under this circumstance, the deceleration circuit 88 will be subjected to the intake manifold vacuum so that the air is drawn from the air chamber 64 through the deceleration air bleed 90 into the deceleration mixture circuit 88. The air flowing through the deceleration mixture circuit 88 creates a suction effect which causes a flow of liquid fuel from the fuel supply chamber 82 through the deceleration fuel jet 92 into the deceleration mixture circuit 88 to form an air-fuel mixture. This air-fuel mixture is admitted through the deceleration port 96 into the main mixture passage 60, and is mixed with the idling air-fuel mixture flowing through the slow running port 74. The resulting air-fuel mixture supplied from the slow running port 74 and the deceleration port 96, which is combustible, is then supplied though the main mixture passage 60 into the balance tube 52 (see FIG. 3), through which the combustible air-fuel mixture is supplied to the intake manifolds 54 of the engine 56.

It will now be understood from the foregoing description that the auxiliary fuel supply system implementing the present invention is capable of supplying the engine with an air-fuel mixture of optimum amount and mixture ratio that are specifically suited for idling and decelerating operations of the engine to eliminate the unburned contents in the engine exhaust gases emitted to the atmosphere.

While one embodiment of the present invention has been herein shown and described in association with the accompanying drawings, it is intended to merely for exemplifying the auxiliary fuel supply system according to the present invention and it should be understood that the auxiliary fuel supply system of the present invention may be modified in many respects without departing from the spirit and scope of the present invention which are defined in the appended claims.

What is claimed is:

1. An auxiliary fuel supply system for use with a multi carburetor system of the variable area venturi type for an internalcombustion engine having an air cleaner, a float chamber, a carburetor induction passage leading from said air cleaner into intake manifolds of said engine, a throttle valve disposed in said carburetor induction passage and adapted to be fully closed during idling and decelerating operations of said engine, a variable area venturi formed in said carburetor induction passage and including a constriction and an air flow control assembly to continuously reduce the effective sectional area at the venturi as said throttle valve closes, and a balance tube connected between said intake manifolds of said engine and commuicating with said carburetor induction passage downstream of said throttle valve, said auxiliary fuel supply system comprising means for defining main passage communicating with said intake manifolds through said balance tube extending therebetween to supply said engine with an air-fuel mixture of optimum amount and mixture ratio for satisfactory combustion when said throttle valve is fully closed during idling and decelerating conditions of said engine, means for defining slow running mixture circuit communicating with said main passage for supplying an air-fuel mixture of optimum mixture ratio through said main passage to said intake manifolds when said throttle valve is fully closed during idling operation of said engine, means for defining deceleration circuit communicating with said main passage for supplying an air-fuel mixture to be mixed with said air-fuel mixture supplied from said slow running mixture circuit to form a combustible air-fuel mixture when said throttle valve is fully closed during decelerat' ing operation of said engine, valve means disposed in said deceleration mixture circuit, and control means responsive to an intake manifold vacuum of said engine for controlling said valve means to open said deceleration circuit when said intake manifold vacuum reaches a predetermined value during decelerating operation of said engine.

2. An auxiliary fuel supply system according to claim 1, wherein said means for defining main passage has a main air inlet leading to an air chamber communicating .with said air cleaner, and a main adjust screw disposed in said main air inlet for controlling the flow of air flowing into said main passage thereby to adjust the mixture ratio of said air-fuel mixture in said main passage.

3. An auxiliary fuel supply system according to claim 1, wherein said means for defining slow running mixture circuit consists of a slow running air bleed vented to the atmosphere and a slow running fuel jet provided upstream of said slow running air bleed and leading to a fuel supply chamber communicating with said float chamber, the effective areas of said slow running air bleed and said slow running fuel jet being determined to admit a suitable amount of air and fuel into said slow running mixture circuit to provide an air-fuel mixture of optimum mixture ratio for the idling operation of said engine.

4. An auxiliary fuel supply system according to claim 3, wherein said slow running mixture circuit includes a slow running port opening to said main passage and a slow running adjust screw disposed therein for controlling the amount of air-fuel mixture to be admitted to said main passagev 5. An auxiliary fuel supply system according to claim 3, wherein said means for defining deceleration mixture circuit consists of a deceleration air bleed leading from said air chamber, and a deceleration fuel jet provided in said deceleration mixture circuit downstream of said deceleration air bleed and communicating with said fuel supply chamber, the effective areas of said deceleration air bleed and said deceleration fuel jet being calibrated to admit air and fuel into said deceleration mixture circuit to provide an air-fuel mixture to be mixed in said main passage with said air-fuel mixture supplied from said slow running mixture circuit to provide a combustible mixture during decelerating operation of said engine.

6. An auxiliaryfuel supply system according to claim 5, wherein said deceleration mixture circuit includes a deceleration port opening to said main passage, said deceleration port being opened and closed by said valve means. diaphragm 7. An auxiliary fuel supply system according to claim 1, wherein said control means includes first and second vacuum chambers, said first vacuum chamber having an outlet passage communicating with said main passage, wall means intervening between said first and second vacuum chambers and having formed therein a valve opening interconnecting said first and second vacuum chambers with respect to each other, first diaphragm means disposed in said first vacuum chamber, a valve element attached to said first diaphragm means and extending through said valve opening formed in said wall means, a first compression spring dispoed in said first vacuum chamber for biasing said first diaphragm means to a position in which said valve element closes said valve opening, a second diaphragm means disposed in said second diaphragm means and having attached thereto said valve means, and a second compression spring disposed in said second vacuum chamber for biasing said second diaphragm means to a position in which said valve means closes said deceleration mixture circuit, said first diaphragm means being moved against the force of said first compression spring to a position in which said valve element opens said valve opening to interconnect said first vacuum chamber with said second vacuum chamber when said intake manifold vacuum reaches a predetermined value, whereby said second diaphragm means is moved against the force of said second compression spring to a position to cause said valve means to open said deceleration mixture circuit.

8. An auxiliary fuel supply system for use with a multi carburetor of the variable area venturi type for an internal combustion engine having an air cleaner, a float chamber, a carburetor induction passage leading from said air cleaner into intake manifolds of said engine, a throttle valve disposed in said carburetor induction passage and adapted to be fully closed during idling and decelerating operations of said engine, a variable area venturi formed in said carburetor induction passage upstream of said throttle valve and consisting of a constriction and an air flow control assembly to continuously reduce the effective sectional area at the venturi as said throttle valve closes, and a balance tube connected between said intake manifolds of saidengine and communicating with said carburetor induction passage downstream of said throttle valve, said auxiliary fuel supply system comprising a body, a fuel supply chamber formed in said body and communicating with said float chamber, an air chamber communicating with said air cleaner, a main mixture passage formed in said body, a main air inlet passage provided upstream side of said main mixture passage and leading from said air chamber, a main adjust screw disposed in said main air inlet passage for controlling the flow of air flowing into said main mixture passage thereby to adjust the mixture ratio of said air-fuel mixture in said main mixture passage, said body being mounted on said balance tube at its intermediate portion to connect said main mixture passage with said intake manifolds, a slow running mixture circuit formed in said body and having a slow running port opening into said main mixture passage, said slow running mixture circuit including a slow running air bleed vented to the atmosphere and a slow running fuel jet provided in said slow running mixture circuit upstream of said slow running air bleed and communicating with said fuel supply chamber, the effective areas of said slow running air bleed and said slow running fuel jet being determined to admit air and fuel in said slow running mixture circuit in an amount to provide an air-fuel mixture of optimum mixture ratio for the idling operation of said engine, a slow running adjust screw disposed in said slow running port to adjust the amount of air-fuel mixture passing therethrough, a deceleration mixture circuit formed in said body and having a deceleration port opening into said main mixture passage, said deceleration mixture circuit including a deceleration air bleed leading from said air chamber and a deceleration fueljet provided in said deceleration mixture circuit downstream of said deceleration air bleed, said deceleration fuel jet communicating with said fuel supply chamber through a deceleration fuel supply passage formed in said body, the effective areas of said deceleration air bleed and said deceleration fuel jet being calibrated to admit air and fuel into said deceleration mixture circuit in an amount to provide an air-fuel mixture which is combustible when mixed in said main mixture passage with said air-fuel mixture supplied from said slow running port, and a control unit associated with said deceleration mixture circuit to control the amount of air-fuel mixture supplied from said deceleration port, said control unit including a housing having formed therein first and second vacuum chambers and having wall portion intervening therebetween, an outlet passage formed in said body for interconnecting said first vacuum chamber with said main mixture passage, said wall portion of said housing having formed with a valve opening which interconnects said first and second vacuum chambers with respect to each other, a cap member attached to one end of said housing, a first diaphragm member interposed between said cap member and the one end of said housing, said cap member having a central aperture constituting atmospheric vent to a chamber formed between said first diaphragm member and the inner surface of said cap member, a first valve element attached to said first diaphragm member and extending into said valve opening, a first compression spring disposed in said first vacuum chamber for biasing said first diaphragm member to a position in which said first valve element closes said valve opening, the other end of said housing being secured to the side wall of said body, a second diaphragm member interposed between the side wall of said body and the other end of said housing, said body being formed with a cavity at the side wall thereof to form a chamber in association with said second diaphragm member, said chamber communicating with said air cleaner, a second valve element attached to said second diaphragm member and exsaid deceleration port.

tending into said deceleration mixture circuit to open and close said deceleration port, and a second compression spring disposed in said second vacuum chamber for biasing said second diaphragm member to a position in which said second valve element closes said deceleration port, said first diaphragm member being responsive to an intake manifold vacuum in said first vacuum chamber, whereby when said intake manifold vacuum exceeds a predetermined value, said first diaphragm member is moved against the force of said first compression spring to a position to cause said first valve element to open said valve opening for thereby causing said second diaphragm member to move against the force of said second compression spring to a position in which said second valve element opens UNITED STATES PATENT OFFICE. V 1 CERTIFICATE OF CORRECTION Patent No. 3,742,922 Dated July 3 1973 Inventor(s) Takashi Hisatomi; Kenichi Sasaki It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Coverin Pa e, Column 1, After "[21] Appl. No. 233,603" and Before [52 insert 1 A "[30] Foreign Application Priority Data A March 11, 1971 Japan. .46-l327l-- Signed Sealed this 5th day of March 197%.

(SEAL) Attest: v

EDWARD M.FLETC HER, JR. 0. MARSHALL DANN A g o f Commissioner of Patents FORM PC1-1050 USCOMM-DC 60376-P69 I Q UTE. GOVERNMENT PRINTING OFFICE I," 0-356-33. A I, 

1. An auxiliary fuel supply system for use with a multi carburetor system of the variable area venturi type for an internal combustion engine having an air cleaner, a float chamber, a carburetor induction passage leading from said air cleaner into intake manifolds of said engine, a throttle valve disposed in said carburetor induction passage and adapted to be fully closed during idling and decelerating operations of said engine, a variable area venturi formed in said carburetor induction passage and including a constriction and an air flow control assembly to continuously reduce the effective sectional area at the venturi as said throttle valve closes, and a balance tube connected between said intake manifolds of said engine and communicating with said carburetor induction passage downstream of said throttle valve, said auxiliary fuel supply system comprising means for defining main passage communicating with said intake manifolds through said balance tube extending therebetween to supply said engine with an air-fuel mixture of optimum amount and mixture ratio for satisfactory combustion when said throttle valve is fully closed during idling and decelerating conditions of said engine, means for defining slow running mixture circuit communicating with said main passage for supplying an air-fuel mixture of optimum mixture ratio through said main passage to said intake manifolds when said throttle valve is fully closed during idling operation of said engine, means for defining deceleration circuit communicating with said main passage for supplying an air-fuel mixture to be mixed with said air-fuel mixture supplied from said slow running mixture circuit to form a combustible air-fuel mixture when said throttle valve is fully closed during decelerating operation of said engine, valve means disposed in said deceleration mixture circuit, and control means responsive to an intake manifold vacuum of said engine for controlling said valve means to open said deceleration circuit when said intake manifold vacuum reaches a predetermined value during decelerating operation of said engine.
 2. An auxiliary fuel supply system according to claim 1, wherein said means for defining main passage has a main air inlet leading to an air chamber communicating with said air cleaner, and a main adjust screw disposed in said main air inlet for controlling the flow of air flowing into said main passage thereby to adjust the mixture ratio of said air-fuel mixture in said main passage.
 3. An auxiliary fuel supply system according to claim 1, wherein said means for definIng slow running mixture circuit consists of a slow running air bleed vented to the atmosphere and a slow running fuel jet provided upstream of said slow running air bleed and leading to a fuel supply chamber communicating with said float chamber, the effective areas of said slow running air bleed and said slow running fuel jet being determined to admit a suitable amount of air and fuel into said slow running mixture circuit to provide an air-fuel mixture of optimum mixture ratio for the idling operation of said engine.
 4. An auxiliary fuel supply system according to claim 3, wherein said slow running mixture circuit includes a slow running port opening to said main passage and a slow running adjust screw disposed therein for controlling the amount of air-fuel mixture to be admitted to said main passage.
 5. An auxiliary fuel supply system according to claim 3, wherein said means for defining deceleration mixture circuit consists of a deceleration air bleed leading from said air chamber, and a deceleration fuel jet provided in said deceleration mixture circuit downstream of said deceleration air bleed and communicating with said fuel supply chamber, the effective areas of said deceleration air bleed and said deceleration fuel jet being calibrated to admit air and fuel into said deceleration mixture circuit to provide an air-fuel mixture to be mixed in said main passage with said air-fuel mixture supplied from said slow running mixture circuit to provide a combustible mixture during decelerating operation of said engine.
 6. An auxiliary fuel supply system according to claim 5, wherein said deceleration mixture circuit includes a deceleration port opening to said main passage, said deceleration port being opened and closed by said valve means. diaphragm
 7. An auxiliary fuel supply system according to claim 1, wherein said control means includes first and second vacuum chambers, said first vacuum chamber having an outlet passage communicating with said main passage, wall means intervening between said first and second vacuum chambers and having formed therein a valve opening interconnecting said first and second vacuum chambers with respect to each other, first diaphragm means disposed in said first vacuum chamber, a valve element attached to said first diaphragm means and extending through said valve opening formed in said wall means, a first compression spring dispoed in said first vacuum chamber for biasing said first diaphragm means to a position in which said valve element closes said valve opening, a second diaphragm means disposed in said second diaphragm means and having attached thereto said valve means, and a second compression spring disposed in said second vacuum chamber for biasing said second diaphragm means to a position in which said valve means closes said deceleration mixture circuit, said first diaphragm means being moved against the force of said first compression spring to a position in which said valve element opens said valve opening to interconnect said first vacuum chamber with said second vacuum chamber when said intake manifold vacuum reaches a predetermined value, whereby said second diaphragm means is moved against the force of said second compression spring to a position to cause said valve means to open said deceleration mixture circuit.
 8. An auxiliary fuel supply system for use with a multi carburetor of the variable area venturi type for an internal combustion engine having an air cleaner, a float chamber, a carburetor induction passage leading from said air cleaner into intake manifolds of said engine, a throttle valve disposed in said carburetor induction passage and adapted to be fully closed during idling and decelerating operations of said engine, a variable area venturi formed in said carburetor induction passage upstream of said throttle valve and consisting of a constriction and an air flow control assembly to continuously reduce the effective sectional area at the venturi as said throttle valve closes, and a balancE tube connected between said intake manifolds of said engine and communicating with said carburetor induction passage downstream of said throttle valve, said auxiliary fuel supply system comprising a body, a fuel supply chamber formed in said body and communicating with said float chamber, an air chamber communicating with said air cleaner, a main mixture passage formed in said body, a main air inlet passage provided upstream side of said main mixture passage and leading from said air chamber, a main adjust screw disposed in said main air inlet passage for controlling the flow of air flowing into said main mixture passage thereby to adjust the mixture ratio of said air-fuel mixture in said main mixture passage, said body being mounted on said balance tube at its intermediate portion to connect said main mixture passage with said intake manifolds, a slow running mixture circuit formed in said body and having a slow running port opening into said main mixture passage, said slow running mixture circuit including a slow running air bleed vented to the atmosphere and a slow running fuel jet provided in said slow running mixture circuit upstream of said slow running air bleed and communicating with said fuel supply chamber, the effective areas of said slow running air bleed and said slow running fuel jet being determined to admit air and fuel in said slow running mixture circuit in an amount to provide an air-fuel mixture of optimum mixture ratio for the idling operation of said engine, a slow running adjust screw disposed in said slow running port to adjust the amount of air-fuel mixture passing therethrough, a deceleration mixture circuit formed in said body and having a deceleration port opening into said main mixture passage, said deceleration mixture circuit including a deceleration air bleed leading from said air chamber and a deceleration fuel jet provided in said deceleration mixture circuit downstream of said deceleration air bleed, said deceleration fuel jet communicating with said fuel supply chamber through a deceleration fuel supply passage formed in said body, the effective areas of said deceleration air bleed and said deceleration fuel jet being calibrated to admit air and fuel into said deceleration mixture circuit in an amount to provide an air-fuel mixture which is combustible when mixed in said main mixture passage with said air-fuel mixture supplied from said slow running port, and a control unit associated with said deceleration mixture circuit to control the amount of air-fuel mixture supplied from said deceleration port, said control unit including a housing having formed therein first and second vacuum chambers and having wall portion intervening therebetween, an outlet passage formed in said body for interconnecting said first vacuum chamber with said main mixture passage, said wall portion of said housing having formed with a valve opening which interconnects said first and second vacuum chambers with respect to each other, a cap member attached to one end of said housing, a first diaphragm member interposed between said cap member and the one end of said housing, said cap member having a central aperture constituting atmospheric vent to a chamber formed between said first diaphragm member and the inner surface of said cap member, a first valve element attached to said first diaphragm member and extending into said valve opening, a first compression spring disposed in said first vacuum chamber for biasing said first diaphragm member to a position in which said first valve element closes said valve opening, the other end of said housing being secured to the side wall of said body, a second diaphragm member interposed between the side wall of said body and the other end of said housing, said body being formed with a cavity at the side wall thereof to form a chamber in association with said second diaphragm member, said chamber communicating with said air cleaner, a second valve element attached to said second diaphragm member and extending into said deceleration mixture circuit to open and close said deceleration port, and a second compression spring disposed in said second vacuum chamber for biasing said second diaphragm member to a position in which said second valve element closes said deceleration port, said first diaphragm member being responsive to an intake manifold vacuum in said first vacuum chamber, whereby when said intake manifold vacuum exceeds a predetermined value, said first diaphragm member is moved against the force of said first compression spring to a position to cause said first valve element to open said valve opening for thereby causing said second diaphragm member to move against the force of said second compression spring to a position in which said second valve element opens said deceleration port. 